/Engine/Source/Runtime/SlateCore/Public/Layout/BasicLayoutWidgetSlot.h
Mixin to add the padding functionality to a base slot that is also a single children.
template<typename MixedIntoType, EInvalidateWidgetReason InPaddingInvalidationReason> class TPaddingSingleWidgetSlotMixin
SlotPaddingAttr...
SlotPaddingAttribute